Range quadrant identification circuit



July 3, 1945. E. NORTON I RANGE QUADRANT IDENTIFICATION CIRCUIT Filed March 3l, 1942 2 Sheets-Sheet 1 RANGE QUADRANT IDENTIFICATION CIRCUIIIT Filed March 31, 1942 2 Sheets-Sheet 2 FIG. Z.

INPI/'' c I 1- FG 5a Vw v /ILV L v /Lv l "ry 16.5d.

Bg @9M Gttorn'eg Patented July 3, 1945 RANGE QUADRAN T IDENTIFICATION CIRCUIT Lowell E. Norton, Collingswood, N; J., assignoi` to Radio Corporation of America, a corporation of Delaware Application March 31, 1942, Serial No. 436,942

(Cl. Z50- 11) 4 Claims.

I'his invention relates-to course and quadrant identiiication in a four course simultaneous radio range, and more particularly to means for giving a Visual quadrant indication which is simple and unmistakable requiring very little interpretation by the pilot. Application Ser. No. 272,017, entitled Radio ranges, filed on May 5, 1.939, by D. G. C. Luck and matured into Patent No. 2,314,795 describes a quadrant identication system in which an auxiliary reference phase tone is radiated non-directionally and compared in phase with the keyed course tone to indicate the quadrant in which the receiver lies. Application Serial No. 436,933, entitled Radio ranges, filed March 31, 1942, by D. G. C. Luck and matured into Patent No. 2,350,284 describes means for attachment to the output of a usual radio range receiver to provide visual indications in such a system by means of two flashing indicator lamps. Another such device, operating on a different principle, is described in application Serial No.

437,149 entitled Radio ranges, led by L. E. Nor ton on April 1, 1942, and matured into Patent No. 2,364,748. A disadvantage of the indicator systems described in said applications is the requirein terms of courses and quadrants. This has been found somewhat difcult, particularly when systems of the type described, and gives a directl indication requiring no mental operation to convert it into usable form. The visual indication ment of interpretation of the keyed light flashes is presented upon a circular screen, divided into l quadrants corresponding to the quadrants of the radio range; the quadrant on the screen corresponding to the range quadrant, in which the receiver is operating, is illuminated by rhythmic flashes. On course, the two quadrants dening the particular course are illuminated.

The invention will be described with reference to the accompanying drawings, of which Figure 1 is a schematic block diagram of the circuit of the device; Figure 2 is a schematic diagram of an adding network'forming a part of the circuit of Figure 1, Figure 3 is a schematic diagram of a .trigger circuit forming a part of the circuit of Figure 1, Figure 4a is a graph of a Voltage pulse of the type occurring in the operation of the system, Figure 4b is a graph of the pulse of Figure 4a after differentiation, Figure 5a is a graph representing radio range N signal, Figure 5b isla graph representing the signal of Figure 5a after integration, Figure `5c is a graph representing the signal of Figure 5a after diierentiation, Figure 5d is a graph representing the sum of the integrated and dierentiated signals of Figures 5b and 5c, respectively, Figure 5e is a graph representing radio range A signal, Figure 5f is a graph representing the signal of Figure 5e after integration, Figure 5g-is a graph representing the signal of Figure 5e after differentiation, and Figure 5h is a graph representing the sum of the integrated and differentiated signals of Figures 5f and 5g, respectively.

Referring to Fig. 1, the quadrant polarity indicator I is a deviceof the type describeciin the above-mentioned Patent No. 2,350,284 and Patent No. 2,364,748. As described in said applications, the four course range transmitter is arranged to radiate non-directionally an auxiliary reference modulation harmonically related to the Course tone modulation. In Ser. No. 436,933 the two modulation frequencies are separated by filters at the receiver. The lower of the two frequencies is multiplied to a frequency equal to that of the other, and the two voltages of the same frequency are compared in phase by means of rectiers arranged to energize one of two circuits, depending on whether said voltages are in phase or out of phase. In Sen-No. 437,139 the combined coursel tone and reference tone modulation is applied to two tubes which are biased by means of a rectifier to a voltage proportional to the average modulation amplitude. The modulation is applied to one of these tubes directly, and to the other tube through a phase shifter which shifts the Ahigher frequency component a predetermined amount with respect to the lower frequency component.

Thus when theratio of peak to average amplitude oi the combined modulation is above a predetermined value, the first tube only will conduct; when said ratio is below the predetermined value, the second tube only will conduct. The circuit designated in Fig. 1 is energized when the receiver is in one of the quadrants arbitrarily chosen as positive, and the circuit is energized in the negative quadrants. This energization is in the forni of keyed impulses A or' N depending on whether the receiver is in an A quadrant or an N quadrant. Thus, in a positive A plied to the receiver are transmitted along the wire, while nothing is'transmitted along the wire. The output from each of the terminals of the quadrant polarity indicator I is divided, andl goes along one path -directly to devices 5, 1, 9,

quadrant, dot-dash impulses ap' and addition devices 5, 1 and 9 are shown ini-f.`

detail in Fig. 2. A signal appliedl to the input is conducted through a resistorl 6-toja1capacitor 8. The voltage developed across the capacitor 8f is proportional to the time integral of the current flowing into it through the resistor 6. very nearly proportional to the time integral. of the voltage applied to the input of the circuit if the magnitude of theresistor Bis large as coinpared to the reactance of the capacitor 8` atthe repetition frequency of the applied potential. The input signal voltage is. also appliedA through the capacitor I0, to the resistor I2, and hence the voltage across it is substantially proportional to the time differential of the inputvoltage if the magnitude of resistor I2 is small as compared to the reactance of the capacitor II] at the repetition frequency of the applied potential. The voltages across the capacitor Sand the resistor I2 are appliedqthrough resistorsV I4 to a resistor I6. Resistors I4 are much higher inresistance than the resistor I6; the current through I6, and hence the voltage across it, is substantially proportional to` the sum of the voltage. across the capacitor 8 and the resistor I2. output terminals,v across the resistor I5, is approximately proportional to thesum of. the time integral and the timeV differential of the signal voltage applied to the input.

Referring again to Fig. 1,.,the output of. each of the addition circutisS is conducted to a peak amplifier II. The peak amplifiers II aremerely single-stage amplifiers biased beyond cut-off, so that they transmit nothing but the peaks of the signalsapplied to their inputs..

'Ihe output of each ofthe. peak. amplifiers II goesto a polarity reverser I3., thence to a trigger stage I5. The circuit of one of the triggerA stages is shown in Fig. 3..` The signal is appliedthrough 'a coupling condenser 23 to. the. grid of. a tube 25.

as compared to the magnitude oi resistor I, atA

the repetition frequency, or4 the applied impulses, so that a signal pulse of.the general shape shown in Fig. 4a will be substantially diierentiated with respect to 'time and produce a diphasic pulse like that shown in Fig. 4b. Theresstor 21 andcapacitor 23 together have` a` relatively longtime constantso for useable valuesof capacitorf23, resistor 21 will bevery large.

In operation, a pulse appliedto, the input first renders the tube conducting, and immediately afterward the tube is cut oi by the. high .negative voltage of the second part of thewaveshownfin- Figueb. The capacitor 23 is chargedwith. thisnegative voltage, which slowly leaks. oithrough.. the resistor 2I and` the Bf supply So thatby the..

This is.`

Thus, the voltage at the time the next pulse arrives, the tube will conduct momentarily and cut off again. During the time the capacitor 23 is charged negatively, the resistance 3l is very high, but when the grid end of the condenser 23 is lpositive, the resistance 3l is low. Thus, any small impulses arriving While the condenser 23 is charged negatively will have no effect atthe output. Pulses applied at timed intervals' however, will cause corresponding pulses in the output circuit.

Each of the trigger stages is connected to an indicator'Iv'I='Which may be an electron ray tube, 'a'. neon lamp, or any voltage operated visual indicating device. The devices I'I are arranged in relative?positionsncorresponding to the four quadrants of" a' radiotjrange, so that ilashing of any one of thenrshows in which of the range quadrantss. the receiver is: located.

Thebperation of the organization of Figure l is'as follows: Depending on the range quadrant, one of: the 1 outpnti leads; oi'. the polarity indicator I is energizedi Witlic a1. keyed'Ai or; N. signal.A First,I assuming that. the: N: signal. is: received', refer to; Fig., 5.. Fig.. 5al represents, the.' conventional N signaliused: in; radio` range; systems. The; dash; iss of onesecondduraticnthef space is one-quarter... the dota is one-quarter secondi and is followed-by* a pause-of one; second; Fig. Slut-shows the result; of integrating. this. signal-'..witlr respect t'c: time.A Fig. 5c, shows;A thev resultar d iierentiating. the.' sigi-l nal with respect. to timex. Fign5dz shows: the' sum: of the, differentiated and, thef integratedl waves., Similarly,n1ligs.` 5e through: 5g; showfan.- A sign'al.. and the; steps resulting; in. the.` VWave of Eig. 571/.. The-,Ng signal is: seenf toproduce a; positive' peakA at the point. cfinfea'chv cycle,.while:theeA. signali produces` negative peaks:` at: the: correspondingpoints. This, difference formsi aa basis? tor.' sepa',- ratin'g. theA, and Nsigna1s..,'I'hus:an A signalaon: the; output -I- oft the '.'polarit-y.' indicator .willf be: conducted.'` to. the:` +A;` and .-I-N. channels.- in. the` diagram of Figure1,;,it.wil1l.b.e integrated; differ.- entiatedg, and` the resultant' potentials. added` by` the-several devices 5,., 1 and` 9'1in.the -I-,N channel, resulting in: negative.: peaks as; shown` in. Fig.. 5h:A

' Since' theV peakmpliers: Irl.' can. pass. only,l posittive peaks, the-:signal-` willi. go: noJ further.` in'. theI +Ni channels. However-due to. the` polarity re1- verserxi in the -I-.As channel; .the signall will. bel inverted to an,.N:,signal;resulting-f in ther. produc,- tion. of: positive peaks atthe'amplienhl inithisy channel,V which will: pass.v to ithe polarity." reverser I3 the trigger. I.5:.andi tha indicator IJz The. polarity reverser I3 is. necessary' to: compensate the-V ).A degree; phase; shift.. or polarity reversal,y caused. bythe singlefstage .peak amplier I I;

. A negative A or N@ signali will be. selectedlin the same;` manner byJ one of the negative channels, causing operationtof: thecorresponding indicator. Thusas unique signal.` is4v actuated in each. quad-` ranti on the-radio range..

Whenuthe receiven is located. on one of." the. course lines., theinterlockingAr andi N4 signalsA together formal. continuousv tone; if both: the A and components areof the same polarity, .the devicesgrLand-"S cannot separatethem; and no indication-isvgiven. This diilculty. is resolved. byusingf a pair' of multivibrators, I9', or otherra laxationf;oscillatorsawhich-are biased so as: tobe. normally non-oscillating.V The. -landv output'.

circuitsepf the .polarity indicator: Irare'eachcon nectedfthrough aV time delay.A networkz 25|.' to. a., control pointl inl the corresponding multivibrator: It.;l As long as thereis no signal, `orf-askeyed siga nale in either; channel., the multivibratorsfremain quiescent. However, when there is a continuous un-keyed signal in either circuit, enough energy gets through the delay circuit 2| to start the corresponding multivibrator I9, which is connected in each case to inject its output in the trigger stages l5 corresponding to the two quadrants which overlap to dene the course, thus actuating the corresponding indicators.

Thus the invention has been described as a device for interpreting the keyed A and N signals of a four course radio range by ilashing one of a group of lights arranged in positions corresponding to the range quadrants. The A and N signals are separated by deriving waves of like shapes but opposite polarities from said signals, and passing the derived waves through positive peak ampliers to trigger circuits controlling the indicators.

While a particular embodiment of the invention has been described it is not intended to limit the scope of the claims to this specic arrangement. For example, an examination of Fig. 5 showsthat the lwave forms of Figs. 5b and 5f diiTer only in polarity and hence may be used to distinguish A and N keying in substantially the manner disclosed above by omitting the diierentiating circuits. A possible disadvantage is the difficulty of adjustment of the apparatus, because the peaks of the waves of Figs. 5b and 5f are much less sharp than those of Figs. 5d and 5h. It is also theoretically possible to omit the integrator circuits, retaining the diiferenti'ators, and

distinguish curves like those shown in Figs. 5c

and 5g. However, the energy content of the extremely sharp peaks of these wave forms is so slight that they are not conveniently usable for controlling the peak amplifiers.

I claim as my invention:

1. In a system for course and quadrant identiiication of a four course simultaneous radio range, quadrant polarity indicator means having two output circuits and responsive to the phase range to provide output in one of said output circuits in response to the eld of said range in a quadrant thereof arbitrarily designated as positive and'output in the other of said output circuits in response to the iield of said range in a quadrant arbitrarily designated as negative, said output being keyed in one of two complementary sequences in accordance with the signals emitted by said range, means connected to each of said output circuits and responsive to output of one of said sequences and an indicator connected thereto, means in each of said channels for converting output of the second of said sequences into output of the first of said sequences, and means connected to each of said converting means and responsive to said converted output and an indicator connected thereto.

2. In a system for course and quadrant identification in a four course simultaneous radio range arranged to emit a non-directional reference phase modulation, quadrant polarity indicator means having two output circuits and responsive to the phase relationship betweenthe signals radiated by said range to provide output in one of said output circuits in response to the eld of said range in a. quadrant thereof arbitrarily designated as positive and output in the relationship between the signals radiated by said other of said output circuits in response to the field of said range in a quadrant arbitrarily designated as negative, said output being keyed in one of two complementary sequences; means connected to each of said output circuits to convert said output into voltages of peaked wave forms having shapes independent of the keying sequence and polarities depending on the keying sequence, means responsive to said peaked wave form voltages in one polarity and an indicator connected thereto; further means connected to each of said output circuits for converting output keyed in one of said sequences into output keyed in the other of said sequences, means connected to each of said convertors for converting the outputs thereof into voltages of peaked wave form having polarities dependent upon the keying sequence of said converted output, means responsive to said second peaked Wave form voltages in one polarity, and an indicator connected thereto.

3. I'he method of distinguishing radio range signals keyed in complementary sequences including the steps of deriving from said signals voltages which vary in accordance with the keying thereof, integrating said voltages with respect to time, differentiating said voltages with respect to time, addingl the results of said integrating and diierentiating operations to produce an impulse having a peaked wave form and a polarity dependent upon the keying sequence of the signal from which it is derived, and producing an indication when said impulse is of a predetermined polarity.

4. A system for course and quadrant identication of a simultaneous radio range of the type arranged to emit a constant non-directional reference modulated signal and two further signals keyed in complementary sequences, said keyed signals being radiated directionally in overlapping figure of eight patterns each having two lobes of opposite polarities arbitrarily designated respectively as positive and negative, including quadrant polarity indication means having two outputl circuits and responsive tothe phase relationship between the iields produced by said non-directional signal and said directional signals to provide output in one of said output circuits in response to the eld of said range in a positive lobe and output in the other of said channels in response to the eld of said range in a negative lobe, said outputs being keyed in accordance with the keying of the signals radiated by said range, four keying sequence responsive circuits, one pair connected to each of said output circuits and each including a differentiating circuit, an integrating circuit, and an adding circuit connected to combine the outputs of said differentiating and integrating circuits to produce a resultant voltage of peaked wave having a shape independent of the keying sequence and a polarity depending upon the keying sequence, four indicator means responsive to voltage peaks of only one polarity, one connected directly to one of each of said pairs of keying sequence responsive circuits, two polarity reversing means, one connected to the other of each of said pairs of keying sequence responsive circuits and to one of the other two of said indicators, respectively.

LOWELL E. NORTON. 

